Nonwoven webs or sheets such as those made of paper find extensive use in modern society in the context of household cleaning activity. Paper towels, for example, are a staple item of commerce which have long been used to wipe up liquid spills and to remove stains and/or soil from hard surfaces such as window glass, countertops, sinks, porcelain and metal fixtures, walls and the like, and from other surfaces such as carpeting or furniture.
Paper towels products which are especially useful for household cleaning have attributes which include relatively low density, high bulk, acceptable softness, high absorbency for both aqueous and nonaqueous liquids and acceptable strength and integrity, especially when wet. Prior art towel products having such attributes, and processes for their preparation, have been disclosed, for example, in Ayers, U.S. Pat. No. 3,905,863, issued Sep. 16, 1975; Ayers, U.S. Pat. No. 3,974,025, issued Aug. 10, 1976; Trokhan, U.S. Pat. No. 4,191,609, issued Mar. 4, 1980; Wells and Hensler, U.S. Pat. No. 4,440,597, issued Apr. 3, 1984; Trokhan, U.S. Pat. No. 4,529,840, issued Jul. 16, 1985; and Trokhan, U.S. Pat. No. 4,637,859, issued Jan. 20, 1987. Paper towels, such as those of the types described in the foregoing patents, are especially useful for absorbing and wiping up liquid spills from both hard surfaces and other surfaces such as furniture and carpets. Paper towel products, however, are also frequently used, generally in combination with liquid cleaning solutions or solvents, to remove soil or stains from surfaces to which such soil or stains may be especially securely affixed. Such soil or stains, for example, may include food material on stove, oven, or cooking utensil surfaces, soap scum found in bathtubs and sinks, food and beverage stains on kitchen counters, ink or crayon markings on walls and furniture, and the like. These prior art materials typically require the consumer to clean soils and stains using a separate cleaning solution and wiping article, which involves a level of inconvenience.
To address this issue of convenience, pre-wetted wiping articles have been developed, particularly in the area of baby wipes. These pre-wetted wipes are typically kept in a dispenser and are typically soaked in a reservoir of a moistening solution. There is often a lack of consistency in terms of the moisture content of each of the wipes, and the wipes feel cold to the touch. Also, because the main purpose of such wipes is to clean, these wipes generally exhibit relatively poor post-cleaning absorbency.
Co-pending U.S. patent application Ser. No. 08/336,456 (hereafter "'456 application"), filed Nov. 9, 1994 by L. Mackey et al., abandoned, discloses and claims wet-like cleansing wipes that are especially useful in removing perianal soils. These cleansing wipes comprise a substrate material (e.g., a nonwoven) that is treated with a water-in-lipid emulsion. These wipes have a number of significant advantages over prior cleaning products, especially when in the form of wet-like cleansing wipes used to remove perianal soils. These articles release significant quantities of water during use for comfortable, more effective cleaning. The continuous lipid phase of the emulsion is sufficiently brittle so as to be easily disrupted by low shear contact (e.g., during the wiping of the skin) to readily release this internal water phase, but sufficiently tough at elevated temperatures where the lipid is melted to avoid premature release of the water phase during the rigors of processing. The continuous lipid phase of these articles is also sufficiently stable during storage so as to prevent significant evaporation of the internal water phase. The normal tensile strength and flushability properties of these articles are not adversely affected when treated with the high internal phase inverse emulsions of the present invention. As a result, users of these articles get comfortable, efficient, moist cleaning without having to change their normal cleaning habits. The application also indicates that the technology is readily useful with other wipes, including wipes for cleaning hard surfaces.
In spite of the significant improvements over prior cleansing wipes, the substrates (also referred to as "carriers") described in the '456 application are lacking in one respect. Specifically, because the carriers described are generally hydrophilic materials, upon shearing of the emulsion in use, a significant amount of water is absorbed into the substrate, and therefore is not available for contact with the item to be cleaned. As such, it is necessary to surface treat the substrate with additional amounts of emulsion to account for the level of water absorbed by the carrier. To address the issue of rapid fluid absorbence by the carrier upon emulsion rupture, co-pending U.S. patent application Ser. No. 08/640,049 (hereafter "'049 application"), filed Apr. 30, 1996 by G. Gordon and L. Mackey, abandoned, describes the use of a carrier that has one or more hydrophobic regions to prevent water absorbence by portions of the substrate. The hydrophobic regions described by this co-pending application are generally described as having permanent hydrophobicity. That is, these regions are essentially unwettable throughout the wiping process and therefore do not contribute significantly to the overall absorbent capacity of the wipe.
Accordingly, in certain circumstances, it would be desirable to provide products for cleaning that offer the benefits provided by the cleansing wipes described in the co-pending '456 application, but which require treatment with reduced levels of emulsion. Similarly, it would be desirable to provide products that have the ability to hinder absorbence such as those described in the co-pending '049 application, but which allow absorbence by essentially all of the carrier. In this regard, a carrier that demonstrates the ability to provide controlled or delayed absorbency may allow for the use of only one carrier material. This would provide, among other things, simplification of processing the wipes, in that a relatively homogeneous carrier could be utilized. Furthermore, the ability to control absorbence of the cleaning solution by the carrier would allow sufficient contact time of the solution on the surface to remove soil, and would allow for the removal of the solution and solubilized soil during the typical wiping process.
Accordingly, it is an object of the present invention to provide nonwoven, preferably paper-based, wiping articles which (i) are initially dry to the touch, but are capable of delivering fluid during the wiping process, (ii) have a controlled rate of absorbency of the fluid released from the article (as well as optional additional cleaning solutions), (iii) have desirably high overall absorbent capacity for liquids and especially effective soil and stain removal performance, and (iv) have sufficient wet strength integrity to withstand the vigors of the wiping process.